Glycol-free aqueous anti-freeze agent containing dicarboxylic salts

ABSTRACT

The present invention relates to an aqueous antifreeze composition comprising 10 to 50% by weight of one or more dicarboxylic acids, preferably aliphatic dicarboxylic acids having 4 to 12 carbon atoms in the form of the alkali metal, ammonium or alkaline earth metal salt. Preferably, these salts are used in combination with at least one further substance. 
     This gives antifreeze compositions with a good frost protective action, good heat conductivity and good protection against corrosion.

This application is the US national phase of international applicationPCT/EP2003/008561 filed 1 Aug. 2003 which designated the U.S. and claimsbenefit of DE 102 35 477.4, dated 2 Aug. 2002, the entire content ofwhich is hereby incorporated by reference.

The present invention relates to aqueous antifreeze compositions basedon dicarboxylic acid salts. These are suitable for use as radiatorantifreezes in combustion engines, for example in motor vehicles, asheat-transfer liquids, for example in solar plants, or as coolingbrines, for example in stationary cooling refrigeration plants.

Antifreeze compositions for the cooling cycles of combustion engines of,for example, automobiles, in most cases comprise alkylene glycols,primarily ethylene glycol and/or propylene glycol, as antifreezecomponent. In addition to other components, corrosion inhibitors, inparticular, are also present.

Particularly in modern combustion engines, thermal stresses are reachedwhich place high requirements on the materials used. Every type and anydegree of corrosion represent a potential risk factor which can lead toa shortening of the service life of the engine and to a reduction inreliability. In addition, in modern engines, a large number of differentmaterials is increasingly used, for example cast iron, copper, brass,soft solder, steel and also magnesium and aluminum alloys. This largenumber of metallic materials additionally gives rise to potentialcorrosion problems, particularly at points where different metals are incontact with one another. At these points in particular it iscomparatively easy for a very wide variety of different types ofcorrosion to arise, for example pitting corrosion, crevice corrosion,erosion or cavitation.

The corrosion protection achieved using the mixtures known to date, andalso the freezing points which can be achieved are generally good.Mixtures of water with alkylene glycols, however, have poorer heatconductivity than water. For this reason, attempts have already longbeen made to develop a glycol-free aqueous coolant formulation, forwhich the addition of salts reduces the freezing point. Numerous patentsand patent applications already exist which propose solutions to thisproblem.

U.S. Pat. No. 2,233,185 describes glycol-free aqueous radiatorantifreezes which contain sodium and potassium salts of so-called “fattyacids” having not more than 9 carbon atoms, for example potassiumformate, acetate and/or propionate for reducing the freezing point.

EP-A 0 306 972 and its equivalent U.S. Pat. No. 5,104,562 describepartially or completely glycol-free, frost-resistant aqueous radiatorantifreezes which comprise potassium formate and acetate for reducingthe freezing point.

DE-A 41 07 442 describes glycol-free aqueous alkali metal salt solutionsbased on acetate/carbonate mixtures as heat-transfer compositions andcoolants.

DE-A 195 10 012 discloses aqueous cooling liquids based on propionicacid salts.

WO 96/26990 describes frost-resistant coolants and heat-transfer liquidswhich comprise mixtures of potassium acetate and formate in addition tocorrosion inhibitors as main components.

EP-A 1 007 600 discloses cooling brines based on alkali metal acetatesand/or formates which, in addition to the customary corrosioninhibitors, additionally comprise alkali metal sulfites.

WO 99/37733 describes glycol-free aqueous cooling liquids with corrosioninhibitors which comprise alkali metal salts of acetic acid and/orformic acid as antifreeze component.

WO 01/94494 describes aqueous cooling liquids with improvedheat-transfer properties based on cesium formate.

WO 01/05906 discloses aqueous formulations for use as radiatorantifreezes and heat-transfer liquids comprising, in addition tocorrosion inhibitors, a mixture of C₁-C₂-carboxylic acid salts,C₃-C₅-carboxylic acid salts and optionally C₆-C₁₂-carboxylic acid salts.The use of dicarboxylic acid salts is not disclosed.

EP-A 0 077 767 describes aqueous antifreeze compositions and deicers, inparticular for the deicing of iced surfaces of roads and paths. Thecompositions comprise, in addition to optional further components whichlower the freezing point, water-soluble salts of one or moredicarboxylic acids having at least three carbon atoms, e.g. mixtures ofadipic, glutaric and succinic acid salts. The formulations are said tobe sometimes useful also for transferring heat and cold in, for example,condensers, radiators and heat exchangers in industry, commercially anddomestically at temperatures of from −20 to +100° C. The dicarboxylicacid salts described in EP-A 0 077 767 are also suitable in theconcentration ranges which are necessary for achieving an adequateantifreeze effect, but they are generally not used in coolants orantifreeze compositions due to the corrosive effect.

Hitherto, no glycol-free coolant or antifreeze composition has beensuccessful in practice despite frequently better heat-transferproperties. This is due, in particular, to the inadequate corrosionprotection, particularly in the case of modern engines, despiteotherwise satisfactory properties with regard to lowering the freezingpoint.

For example, the often proposed formates and acetates are in practiceextremely corrosive. There is therefore a need for a glycol-free coolantwith at least comparable corrosion protection as the knownglycol-containing formulations.

It is an object of the present invention to provide such antifreezecompositions/coolants which do not have the disadvantages of the priorart. These mixtures should have a balanced relationship of theproperties corrosion protection, heat transfer and frost resistance. Inparticular, an improved heat conductivity compared with theglycol-containing antifreeze compositions known hitherto should result.

We have found that this object is achieved by an aqueous antifreezecomposition comprising 10 to 50% by weight of one or more salts from thegroup of saturated and unsaturated, aliphatic and aromatic dicarboxylicacids in the form of the alkali metal, ammonium or alkaline earth metalsalt, further comprising one or more customary corrosion-inhibitingsubstances used in aqueous coolants.

We have found that this object is also achieved through the use asantifreeze composition of a salt of a dicarboxylic acid from the groupof saturated and unsaturated, aliphatic and aromatic dicarboxylic acidsin the form of the alkali metal, ammonium or alkaline earth metal salt,in combination with one or more customary corrosion-inhibiting substanceused in aqueous coolants.

It is in particular advantageous to use the said combination in coolingliquids, heat transfer liquids or cooling brines.

By combining customary corrosion-inhibiting agents with dicarboxylicacid salts, which, in relatively high concentrations, otherwise have avery corrosive action, their corrosive effect is surprisinglysuppressed. In this combination, dicarboxylic acid salts lend themselvesas antifreeze composition. This way is not only a good protectionagainst freezing with an ice flocculation point according to ASTM D 1177of less than −30° C. achieved in the antifreeze compositions accordingto the invention, but also excellent heat conductivity combined withvery good corrosion protection.

Examples of aromatic dicarboxylic acids include phthalic acid andterephthalic acid.

Preference is given to using the salts of unbranched or branched,saturated or unsaturated aliphatic dicarboxylic acids having 2 to 15carbon atoms or mixtures thereof. Acids of this class suitable accordingto the invention include oxalic acid, malonic acid, succinic acid,glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid,sebacic acid, undecanedioic acid, dodecanedioic acid, maleic acid,fumaric acid, sorbic acid. Mixtures of carboxylic acids which areproduced industrially, as are marketed, for example, under the nameSokalan® DCS(C₄-C₆-dicarboxylic acids) from BASF AG, can also be usedaccording to the invention.

In particular, linear saturated, aliphatic dicarboxylic acids having 4to 12 carbon atoms or mixtures thereof are used, an example of whichbeing Sokalan® DCS. The use of salts of adipic acid is most preferred.

All of the abovementioned carboxylic acids are present in the antifreezecompositions according to the invention in the form of an alkali metalsalt, preferably a sodium or potassium salt, or in the form of anammonium salt or substituted ammonium salt, for example in the form ofammonia, trialkylamines or trialkanolamines. The salts are usually inthe form of the bis salts, but can also be in the form of monosalts ofthe dicarboxylic acids, or of mixtures of bis- and monosalts.

In a preferred embodiment of the present invention, thecorrosion-inhibiting substance used is one or more compounds from thegroups listed below.

-   a) 0.01 to 5% by weight of one more compounds from the group of    aliphatic and aromatic monocarboxylic acids having 3 to 16 carbon    atoms in the form of their alkali metal, ammonium and substituted    ammonium salts;-   b) 0.01 to 5% by weight of one or more compounds from the group of    aliphatic and aromatic di- and tricarboxylic acids each having 3 to    21 carbon atoms in the form of their alkali metal, ammonium and    substituted ammonium salts, where, in cases where a dicarboxylic    acid is used, this is different from the dicarboxylic acid used as    antifreeze composition;-   c) 0 to 1% by weight of one or more compounds from the group of    alkali metal borates, alkali metal phosphates, alkali metal    silicates, alkali metal nitrites, alkali metal and alkaline earth    metal nitrates, molybdates and alkali metal and alkaline earth metal    fluorides;-   d) 0 to 1% by weight of one or more compounds from the group of    hard-water stabilizers based on polyacrylic acid, polymaleic acid,    acrylic acid-maleic acid copolymers, polyvinylpyrrolidone,    polyvinylimidazole, vinylpyrrolidone-vinylimidazole copolymers and    copolymers of unsaturated carboxylic acids and olefins;-   e) 0.01 to 5% by weight of one or more compounds from the group of    carboxamides and sulfonamides;-   f) 0.01 to 5% by weight of one or more compounds from the group of    mono- and binuclear unsaturated and partially unsaturated    heterocycles having 4 to 10 carbon atoms, which may be benzo-fused    or carry additional functional groups,-   g) 0.01 to 5% by weight of one or more compounds from the group of    tetra(C₁-C₈-alkoxy)silanes (orthosilicic acid tetra-C₁-C₈-alkyl    esters);-   h) 0.01 to 5% by weight of one or more compounds from the group of    aliphatic, cycloaliphatic and aromatic amines having 2 to 15 carbon    atoms which may additionally contain ether oxygen atoms or hydroxyl    groups.

It is possible to use one or more compounds from each of the groups ofsubstances a) to h) listed above. The substances additionally used canoriginate from one or more of the groups of substances a) to h).

Examples of linear, branched and cyclic aliphatic monocarboxylic acidsof group a) include propionic acid, pentanoic acid, hexanoic acid,cyclohexylacetic acid, octanoic acid, 2-ethylhexanoic acid, nonanoicacid, isononanoic acid, decanoic acid, undecanoic acid and dodecanoicacid.

Examples of aromatic carboxylic acids of group a) include benzoic acidand substituted benzoic acid. Examples thereof includeC₁-C₈-alkylbenzoic acid, in particular o-, m- and p-methylbenzoic acidand p-tert-butylbenzoic acid, and hydroxyl-containing aromaticmonocarboxylic acids, in particular o-, m- and p-hydroxybenzoic acid ando-, m- and p-(hydroxymethyl)benzoic acid and halobenzoic acids, inparticular o-, m- and p-fluorobenzoic acid and benzoic acid substitutedby nitro groups, in particular o-, m- and p-nitrobenzoic acid. The useof unsubstituted benzoic acid is preferred.

Examples of di- and tricarboxylic acids of group b) include malonicacid, succinic acid, glutaric acid, adipic acid, pimelic acid, subericacid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioicacid, dicyclopentadienedicarboxylic acid, phthalic acid, terephthalicacid and triazinetriiminocarboxylic acids, for example6,6′,6″-(1,3,5-triazine-2,4,6-triyltriimino)trihexanoic acid.

The carboxylic acids specified above under a) and b) are in the form ofalkali metal salts, preferably sodium or potassium salts, or ammonium orsubstituted ammonium salts (amine salts), for example of ammonia,trialkylamines or alkanolamines. Corresponding imides of thedicarboxylic acids can also be used.

Examples of compounds specified under c) are sodium tetraborate (borax),disodium hydrogenphosphate, trisodium phosphate, sodium metasilicate,sodium nitrite, sodium nitrate, magnesium nitrate, sodium fluoride,potassium fluoride, magnesium fluoride and sodium molybdate. Saidcompounds have corrosion-inhibiting properties. If alkali metalsilicates are co-used, these are expediently stabilized by customaryorganosilicophosphonates or organosilicosulfonates in customary amounts.

In addition to said inhibitor components, additives, for example solublesalts of magnesium of organic acids, for example magnesiumbenzenesulfonate, magnesium methanesulfonate, magnesium acetate ormagnesium propionate, hydrocarbazoles or quaternized imidazoles, as aredescribed in DE-A 196 05 509, can, for example, also be used incustomary amounts. Sulfites as are disclosed in EP-A 1 007 600 can alsobe used.

Examples of carboxamides and sulfonamides of group e) include aliphatic,cycloaliphatic, aromatic and heteroaromatic carboxamides andsulfonamides each having 2 to 16 carbon atoms, preferably each having 3to 12 carbon atoms.

Examples of the abovementioned carboxamides and sulfonamides are listedbelow:

-   Benzamide, 2-methylbenzamide, 3-methylbenzamide, 4-methylbenzamide,    2,4-dimethylbenzamide, 4-tert-butylbenzamide, 3-methoxybenzamide,    4-methoxybenzamide, 2-aminobenzamide (anthranilamide),    3-aminobenzamide, 4-aminobenzamide, 3-amino-4-methylbenzamide,    2-chlorobenzamide, 3-chlorobenzamide, 4-chlorobenzamide,    2-fluorobenzamide, 3-fluorobenzamide, 4-fluorobenzamide,    2,6-difluorobenzamide, 4-hydroxybenzamide, 2-hydroxybenzamide,    (salicylamide), phthaldiamide, terephthaldiamide, nicotinamide    (pyridine-3-carboxamide), picolinamide (pyridine-2-carboxamide),    succinamide, adipamide, propionamide, hexanamide, 2-pyrrolidone,    N-methyl-2-pyrrolidone, 2-piperidone, ε-caprolactam,    benzenesulfonamide, o-toluenesulfonamide, m-toluenesulfonamide,    p-toluenesulfonamide, 4-tert-butylbenzenesulfonamide,    4-fluorobenzenesulfonamide, 4-hydroxybenzene-sulfonamide,    2-aminobenzenesulfonamide, 3-aminobenzenesulfonamide,    4-aminobenzenesulfonamide, 4-acetylbenzenesulfonamide.

The amides of group e) can optionally be alkyl-substituted on thenitrogen atom of the amide group, for example by a C₁-C₄-alkyl group.Aromatic or heteroaromatic basic structures of the molecule canobviously also carry such alkyl groups. In the molecule, one or more,preferably one or two, amide groups may be present. The amides canadditionally have functional groups, preferably from the groupC₁-C₄-alkoxy, amino, fluorine, chlorine, hydroxyl and acetyl. Theabovementioned functional groups are present in particular assubstituents on different aromatic and heteroaromatic rings.

Examples of heterocycles of group f) include mononuclear five- andsix-membered systems having 1, 2 or 3 nitrogen atoms or having onenitrogen atom and one sulfur atom, where said systems may bebenzo-fused. It is also possible to use binuclear systems of five- orsix-membered part rings typically having 2, 3 or 4 nitrogen atoms. Theheterocycles f) can carry additional functional groups, preferably fromthe group consisting of C₁-C₄-alkoxy, amino and mercapto. Theheterocyclic basic structure can of course be substituted by alkylgroups.

Preferred heterocycles f) include benzotriazole, tolutriazole,hydrogenated tolutriazole, 1H-1,2,4-triazole, benzimidazole,benzthiazole, adenine, purine, 6-methoxypurine, indole, isoindole,isoindoline, pyridine, pyrimidine, 3,4-diaminopyridine,2-aminopyrimidine and 2-mercaptopyrimidine.

Examples of tetra(C₁-C₈-alkoxy)silanes of group g) includetetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane ortetra-n-butoxysilane.

Examples of aliphatic, cycloaliphatic and aromatic amines of group h)having 2 to 15 carbon atoms, which may additionally contain ether oxygenatoms or hydroxyl groups, include ethylamine, propylamine,isopropylamine, n-butylamine, isobutylamine, sec-butylamine,tert-butylamine, n-pentylamine, n-hexylamine, n-heptylamine,n-octylamine, isononylamine, di-n-propylamine, diisopropylamine,di-n-butylamine, mono-, di- and triethanolamine, piperidine, morpholine,aniline and benzylamine. Aliphatic and cycloaliphatic amines h) arepreferably saturated. Preference is given to the use of amines having 4to 8 carbon atoms.

The pH of the antifreeze compositions according to the invention isusually in the range from 6 to 11, preferably 6 to 10, in particular 7to 9.5. In this connection, the desired pH can, where appropriate, beestablished also by adding alkali metal hydroxide, ammonia or amines tothe formulation, solid sodium hydroxide or potassium hydroxide and alsoaqueous sodium hydroxide or potassium hydroxide solutions beingparticularly suitable for this purpose. Carboxylic acids to be usedconcomitantly are expediently added at the same time as thecorresponding alkali metal salts in order that they are automatically inthe desired pH range. It is however, also possible to add the carboxylicacids as free acids and then to neutralize with alkali metal hydroxide,ammonia or amines, and establish the desired pH range.

In general, the antifreeze compositions according to the invention donot comprise any glycol.

In one embodiment, the aqueous antifreeze compositions according to theinvention also comprise small amounts, in particular less than 10% byweight, of ethylene glycol or propylene glycol or mixtures of alkyleneglycols or of glycerol with ethylene glycol or propylene glycol. For thepurposes of the present invention, “propylene glycol” is understood asmeaning both 1,2-propylene glycol and also 1,3-propylene glycol.

In a further embodiment, the aqueous antifreeze compositions accordingto the invention may also comprise small amounts, less than 10% byweight and in particular less than 5.5% by weight, of polyethyleneglycols and/or polypropylene glycols having 2 to 15 glycol ether units,such as, for example, diethylene glycol, triethylene glycol,tetraethylene glycol, dipropylene glycol, tripropylene glycol andtetrapropylene glycol. Corresponding water-soluble alkylene glycol orpolyalkylene glycol ethers may also be present in the given amounts,such as, for example, triethylene glycol monomethyl ether.

As further customary auxiliaries, the antifreeze compositions accordingto the invention can comprise, in customary low amounts, also antifoam,generally in amounts of from 0.001 to 0.010% by weight, individual ortwo or more dyes, and bitter substances for reasons of hygiene andsafety in the case of swallowing. One example of a suitable bittersubstance is denatonium benzoate. The dyes mentioned are preferablychosen from the group consisting of C.I. Direct Blue 199 (C.I. 74190),C.I. Direct Blue 86 (C.I. 74180), C.I. Acid Green 25 (C.I. 61570), C.I.Acid Yellow 73 (C.I. 45350), C.I. Reactive Violet 5 (C.I. 18097) andUranine (sodium fluorescein) and mixtures thereof.

The formulations according to the invention can also additionallycomprise one or more inorganic or organic substances which lower thefreezing point, for example formates, acetates and/or propionates, asare known from the prior art. In principle, mixtures with glycol-freeand glycol- or glycerol-containing radiator antifreezes are alsopossible.

The aqueous antifreeze compositions according to the invention haveprimarily a considerably better corrosion inhibition compared with thecompositions known from the prior art. This action is particularly goodfor the combination of the dicarboxylic acid salts according to theinvention with one or more substances from the groups a) to h). Evenmore preferred is the combination of one or more substances from thegroups a), b), c), d) and/or f). Particular preference is given to theuse of salts of 2-ethylhexanoic acid, p-hydroxybenzoic acid, benzoicacid, isononanoic acid, sebacic acid or dodecanedicarboxylic acid, andof tolutriazole, benzotriazole, 1H-1,2,4-triazole, sodium molybdate andsodium metasilicate.

The aqueous solutions based on dicarboxylic acid salts are suitable foruse as radiator antifreezes for combustion engines, for example in motorvehicles or ships. In addition, they are suitable as heat-transferliquids, for example for the operation of solar plants, for example ofprivate or public buildings for obtaining hot water or as coolingbrines, for example in stationary cooling plants such as, for example,in cold or frozen storage depots for storing foods, the use as radiatorcoolant for combustion engines being preferred.

The examples below serve to illustrate the invention without limitingit.

EXAMPLES

The novel aqueous radiator antifreezes according to the invention can inprinciple be prepared by simply mixing and dissolving the feedsubstances in water, which is described below by way of example forexample 1:

Example 1 Quantitative Ratios of the Feed Substances According to Table1

Distilled water is firstly admixed with adipic acid and, by adding 50%strength KOH, dissolved with stirring. To this solution is then added asecond solution which has been prepared beforehand from distilled water,50% strength KOH, dodecanedicarboxylic acid and sodiummetasilicate×5H₂O/sodium silicophosphonate mixture. To this is then alsoadded 2-ethylhexanoic acid, 4-hydroxybenzoic acid, benzotriazole andtolutriazole, giving a clear solution with a pH of 9.

Table 1 lists the feed substances of examples 1 to 4 according to theinvention.

TABLE 1 Feed substances Exam- Exam- Exam- Exam- Exam- [% by wt.] ple 1ple 2 ple 3 ple 4 ple 5 Adipic acid 27.45 24.00 24.00 27.45 Sokalan ®DCS 27.00 H₂O 27.06 26.14 33.19 28.46 23.56 KOH, 50% in H₂O 44.44 41.7439.00 43.04 44.44 Tripropylene glycol 3.50 2-Ethylhexanoic acid 0.583.50 1.00 0.58 0.58 p-Hydroxybenzoic acid 0.21 0.21 Benzoic acid 0.21Dodecanedicarboxylic 0.03 0.03 0.03 acid Tolutriazole 0.05 2.42 0.500.50 0.05 Benzotriazole 0.05 0.05 0.05 Sodium molybdate × 2.20 2.20 2H₂OSodium metasilicate × 0.11 0.10 0.11 0.11 5H₂O Sodium 0.02 0.01 0.020.02 silicophosphonate

Tables 2 and 3 show corrosion results of the formulations according tothe invention and comparative examples 1 and 2 in the GlasswareCorrosion Test in accordance with ASTM D 1384-97 and in the Static HotCorrosion Test in accordance with ASTM D 4340.

As can be seen, the novel aqueous radiator antifreezes according to theinvention achieve very good freezing protection (ice flocculation pointssee table 2) coupled with excellent corrosion protection for a very widevariety of metal alloys, which overall is significantly better than theprior art hitherto for glycol-free coolants.

TABLE 2 Glassware Corrosion Test in accordance with ASTM D 1384-97Coolant protectant tested (concentration: 100% by volume) Comparison 1Comparison 2 (WO 01/05906, (EP 0 077 767, Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5Ex. 2) Ex. 1) Ice flocculation −37 −35 −30 <−35 <−35 −25 to −34 <−35points [° C.] acc. to ASTM D 1177: Weight changes: [mg/cm²] [mg/cm²][mg/cm²] [mg/cm²] [mg/cm²] [mg/cm²] [mg/cm²] Test bodies Copper −0.09−0.15 0.01 −0.12 −0.04 −0.16 +0.15 Soft solder 0.03 0.01 0.02 −0.23−0.06 −4.89 −25.37 Glass −0.06 −0.32 0.03 −0.11 0.02 −0.17 +0.14 Steel0.02 0.02 0.00 0.00 0.02 0.01 −1.18 Gray iron 0.04 0.02 0.06 0.02 −0.01−4.18 −35.30 Cast aluminum 0.02 0.05 −0.03 −0.01 0.00 −0.19 −0.69Appearance of clear clear clear clear clear cloudy very brown coolantafter precipitations test:

TABLE 3 Static hot corrosion test in accordance with ASTM D 4340-98Radiator antifreeze tested (concentration: 100% by volume): Example 1Example 2 Example 5 Weight changes: [mg/cm²/week] [mg/cm²/week][mg/²/week] Test bodies: Cast aluminum −0.28 −0.19 −0.13

1. An aqueous antifreeze composition comprising 10 to 50% by weight ofat least one alkali metal, ammonium or alkaline earth metal salt of alinear saturated aliphatic dicarboxylic acid having 4 to 12 carbonatoms, at least one corrosion-inhibiting substance for aqueous coolants,one or more alkali metal silicates, and (a) 0.01 to 5% by weight of onemore compounds from the group of aliphatic monocarboxylic acids having 3to 16 carbon atoms in the form of their alkali metal, ammonium andsubstituted ammonium salts, wherein the one or more alkali metalsilicates is present in the aqueous antifreeze composition in an amountof up to 1% by weight.
 2. An antifreeze composition as claimed in claim1, wherein the salt is a sodium or potassium salt, an ammonium,trialkylamine or trialkanolamine salt.
 3. An antifreeze composition asclaimed in claim 1, wherein the composition further comprises one ormore compounds from the groups listed b) through h) below: b) 0.01 to 5%by weight of one or more compounds from the group of aliphatic andaromatic di- and tricarboxylic acids each having 3 to 21 carbon atoms inthe form of their alkali metal, ammonium and substituted ammonium salts,where, in cases where a dicarboxylic acid is used, this is differentfrom the dicarboxylic acid used as antifreeze composition; c) 0 to 1% byweight of one or more compounds from the group of alkali metal borates,alkali metal phosphates, alkali metal nitrites, alkali metal andalkaline earth metal nitrates, molybdates and alkali metal and alkalineearth metal fluorides; d) 0 to 1% by weight of one or more compoundsfrom the group of hard-water stabilizers based on polyacrylic acid,polymaleic acid, acrylic acid-maleic acid copolymers,polyvinylpyrrolidone, polyvinylimidazole,vinylpyrrolidone-vinylimidazole copolymers and copolymers of unsaturatedcarboxylic acids and olefins; e) 0.01 to 5% by weight of one or morecompounds from the group of carboxamides and sulfonamides; f) 0.01 to 5%by weight of one or more compounds from the group of mono- and binuclearunsaturated and partially unsaturated heterocycles having 4 to 10 carbonatoms, which may be benzo-fused or carry additional functional groups;g) 0.01 to 5% by weight of one or more compounds from the group oftetra(C₁-C₈-alkoxy)silanes (orthosilicic acid tetra-C₁-C₈-alkyl esters);h) 0.01 to 5% by weight of one or more compounds from the group ofaliphatic, cycloaliphatic and aromatic amines having 2 to 15 carbonatoms which may additionally contain ether oxygen atoms or hydroxylgroups.
 4. An antifreeze composition as claimed in claim 3, wherein thecomposition comprises a combination of one or more substances from thegroups a), b), c), d) and/or f).
 5. An antifreeze composition as claimedin claim 4, wherein the composition comprises a combination of one ormore substances from groups a), b), c) and f), wherein a) is2-ethylhexanoic acid, p-hydroxybenzoic acid, benzoic acid, orisononanoic acid, b) is sebacic acid or dodecanedicarboxylic acid, c) issodium molybdate, and f) is tolutriazole, benzotriazole or1H-1,2,4-triazole.
 6. An antifreeze composition as claimed in claim 1,wherein the composition pH is in the range from 6 to
 11. 7. Anantifreeze composition as claimed in claim 1, which comprises less than10% by weight of ethylene glycol, propylene glycol, polyethylene glycolsand/or polypropylene glycols having 2 to 15 glycol ether units.
 8. Anantifreeze composition as claimed in claim 1, wherein the alkali metalsilicate is sodium metasilicate.